One of the advantages of caller ID is that when someone calls, the called party is able to know who is calling. This allows the called party to make a better decision on whether to answer the call. For example, if the called party knows that the calling party is someone important, the called party is likely to answer the call. On the other hand, if the calling party is someone who the called party may not want to talk to, the called party may be less likely to answer the incoming call. The ability to screen calls based on who is calling is ubiquitous in today's telephony systems.
However, the caller ID model breaks down if the calling party is part of a prior call or involved in a conference call. For example, if Joe and Sally are engaged in a call and Sally calls Ted to conference Ted into the call, Ted will only receive the caller ID of Sally. Ted does not know that Joe is also one of the calling parties. In this example, the called party is not provided the full list of who is actually calling. What is needed is a solution that identifies all the calling parties who are part of an incoming call. This allows the called party to screen these types of calls in the same way they can screen a call from a single party.